A major effort will be directed towards documentation of the phenomenon of an increased efficacy of O23Opsi to improve results of radiation therapy of murine tumors by use of pentobarbital anesthesia. This will mean examination for such an effect using early generation isotransplants of 4 of the spontaneous tumors in this laboratory. These include two squamous cell carcinomas and two fibrosarcomas. This will be in addition to the work with spontaneous mammary carcinoma. In addition, efforts will be directed towards evaluation of the mechanism of this effect: examination for the role of hypothermia (pentobarbital induces a hypothermia of about 4-6 degrees C), changes in blood flow (using rubidium extraction technique) and to assess the efficacy of anesthesia effect against oxygen produced lung damage. Studies will be made on the efficacy of combining oxygen at normal or increased pressure to improve the enhancement ratio of misonidazole in treatment of murine tumors. Further, we will perform additional assay to evaluate therapeutic gain factors for fast neutrons versus O2 at 3Opsi and misonidazole. The fast neutron radiation will be performed using the Naval Research Laboratory cyclotron at Washington.